The present invention is directed to a multiple re-entry implantable septum and a method of using the same. The implantable septum and method are suitable for use in conjunction with an implantable infusion device and the drug reservoir therefor.
With implantable infusion devices currently marketed, drugs to be infused into the human body are stored in a reservoir that is contained within a body cavity. To place drugs into the reservoir, it is necessary to pierce an inlet septum with a needle introduced percutaneously. The surface area of the septum available for puncture can be directly correlated to the ease of needle placement and the duration of time the septum can maintain its integrity. A large surface area will make locating of the septum under the skin easier; however, more stress will be applied to the resilient septum with each puncture than with a smaller surface area.
Certain currently available septa used in conjunction with implantable infusion devices consist of a solid piece of molded rubber force-fit into an inlet port, see U.S. Pat. Nos. 4,190,048; 4,193,397; and 4,360,019, for example. The force-fit assures that the rubber is placed in compression and, thus, punctures made through the rubber will be effectively sealed as the rubber expands to fill the space left by the passage of the needle. Such septa work well in limited use, disposable applications, but can become ineffective when repetitively punctured.
Chronic implantation of an infusion device will necessitate numerous punctures of the septum. Over an extended period of time, these perforations could result in uncontrolled and unmonitored leakage of the intended infusate through the septum into the body cavity. Depending upon the drug and its concentration, this situation could result in serious harm to the patient.
Thus, an object of the present invention is to provide an improved implantable septum which can be entered numerous times without compromising its mechanical stability or patient safety.
Another object of the invention is to provide an improved multiple re-entry implantable septum which can be easily located under the skin and which facilitates the placement of the needle into the septum.
These and other objects of the invention are attained by providing a multiple re-entry implantable septum comprising a casing and a resilient member positioned within the casing. The resilient member has a perforation therein which is compressed closed at least when the member is positioned within the casing. An outer side of the casing has a relatively large surface configured to channel the end of a slender, elongate component such as a needle to a predetermined location at a relatively small bore in the outer side of the casing which is located adjacent the perforation in the resilient member.
The size of the relatively small bore in the casing is smaller than the diameter of a needle of a first gauge so as to prevent the needle from passing through the bore, but is larger than a smaller diameter needle of a second gauge to permit the second needle to pass through the bore of the casing and the perforation of the resilient member.
In the disclosed embodiment, the casing is connected to an implantable drug reservoir for an implantable drug infusion device with multiple re-entry to the reservoir for filling the same being obtained via the small bore in the casing and the perforation in the resilient member. The resilient member is a silicone rubber or polyurethane molding perforated with a narrow bore hole. The resilient member is preferably force-fit into the casing so as to compress the member and close the bore hole therein.
The method of using the septum of the invention comprising providing an assembly of a first needle and a cannula positioned over the first needle, penetrating the skin with the first needle and cannula thereon and contacting the surface of the casing with the end of the needle so as to channel the needle to the small bore in the casing. The small bore is dimensioned to prevent passage of the first needle through the casing. The first needle is then withdrawn from the casing and skin, while leaving the cannula in place adjacent the small bore in the casing. A second, relatively smaller needle is then inserted into the cannula and through the small bore of the casing and the perforation in the resilient member. The second needle is attached to a syringe for filling the drug reservoir.
Since the needle will enter the septum through the same opening each time, and that opening will have been formed in the manufacturing process, no destruction of the silicone rubber or polyurethane member will occur due to punctures. In addition, the stress that is inflicted on the currently available septa due to punctures will be eliminated.
The protective shroud or casing over the resilient member also enables the implanted septum to be easily located under the skin and facilitates the placement of the needle into the septum. Therefore, the two most undesirable characteristics of implantable septum, material destruction leading to possible failure to contain liquid in the reservoir, and difficulty in locating the septum, are circumvented by the improved implantable septum of the invention.
These and other objects, features and advantages of the present invention will become more apparent from the following description when taken in connection with the accompanying drawings which show, for purposes of illustration only, one preferred embodiment in accordance with the present invention.